Integration Test For Hosted Service .Net-Core`

Question

I have a QueueTask Hosted service (.Net-Core\'s new background service) that I\'d like to test. My queuedHosted service looks like so:

public QueuedHostedSe         


        

Answer 1

Hosted services are started by the framework as part of the WebHost's start process

// Fire IHostedService.Start
await _hostedServiceExecutor.StartAsync(cancellationToken).ConfigureAwait(false);

Source

via the HostedServiceExecutor which would take a collection of all the registered IHostedService, enumerate them and start them in turn

public HostedServiceExecutor(ILogger<HostedServiceExecutor> logger, IEnumerable<IHostedService> services)
{
    _logger = logger;
    _services = services;
}

public async Task StartAsync(CancellationToken token)
{
    try
    {
        await ExecuteAsync(service => service.StartAsync(token));
    }
    catch (Exception ex)
    {
        _logger.ApplicationError(LoggerEventIds.HostedServiceStartException, "An error occurred starting the application", ex);
    }
}

Source

But since you are testing the hosted service on its own, you have to act as the framework and start the service yourself.

[TestMethod]
public async Task Verify_Hosted_Service_Executes_Task() {
    IServiceCollection services = new ServiceCollection();
    services.AddSingleton<ILoggerFactory, NullLoggerFactory>();
    services.AddHostedService<QueuedHostedService>();
    services.AddSingleton<IBackgroundTaskQueue, BackgroundTaskQueue>();
    var serviceProvider = services.BuildServiceProvider();

    var service = serviceProvider.GetService<IHostedService>() as QueuedHostedService;

    var backgroundQueue = serviceProvider.GetService<IBackgroundTaskQueue>();

    await service.StartAsync(CancellationToken.None);

    var isExecuted = false;
    backgroundQueue.QueueBackgroundWorkItem(async (sp, ct) => {
        isExecuted = true;
    });

    await Task.Delay(10000);
    Assert.IsTrue(isExecuted);

    await service.StopAsync(CancellationToken.None);
}